# common.py

def do_index_class(index):

    """自定义过滤器"""

    if index == :

        return "first"

    elif index == :

        return "second"

    elif index == :

        return "third"

    else:

        return ""

from info.utils.common import do_index_class

# 添加自定义过滤器

app.add_template_filter(do_index_class, "index_class")

{% for news in data.click_news_list %}

    <li><span class="{{ loop.index0 | indexClass }}">{{ loop.index }}</span></li>

{% endfor %}

@app.route('/')

def index():

    data = {

        "click_news_list": ['aaa', 'bbb','ccc'],

    }

    return render_template('./index.html', data=data)

.first{

    background: #f33;

    color:#fff;

}

.second{

    background:#ff722b;

    color:#fff;

}

.third{

    background:#fa3;

    color:#fff;